Fix make Bluetooth discoverable without additional permission

- Only enable device can be discoverable when the user launch
  "Connected Devices settings" through settings and systemui

Bug: 194695497
Test: make -j42 RunSettingsRoboTests and use test apk to manually test
to verify the device is not discoversable when open "Connected settings"
through test apk.

Change-Id: Ia04ab759b737acf30b782f5c5831dd59f25fb257